Hyperadrenocorticism affects many adult dogs. Whether the disease is pituitary-dependent (80% to 85% of spontaneous cases) or adrenal-dependent (15% to 20% of cases), the clinical and laboratory abnormalities associated with it result from chronic hypercortisolemia. Clinical signs of hyperadrenocorticism at the time of diagnosis can vary widely, and they develop so gradually that owners often mistake the signs for "normal" aging. Being aware of the more subtle signs of canine hyperadrenocorticism can be key to early diagnosis and initiation of therapy.

Whenever possible, pituitary-dependent hyperadrenocorticism and adrenal tumors should be differentiated to help guide therapy and patient monitoring. Early diagnosis and management of canine hyperadrenocorticism may not only improve the patient's clinical signs but may also keep the more severe consequences of Cushing's syndrome from developing.

Mitch was presented to his primary care veterinarian for evaluation of polyuria and polydipsia of six months' duration. The dog's urine specific gravity was 1.010 and a serum chemistry profile revealed an alkaline phosphatase activity of 1,240 IU/L (reference range 37 to 105 IU/L). The results of a complete blood count were within normal limits, and urine bacterial culture results were negative.

The abnormal LDDS eight-hour cortisol concentration, in combination with more than 50% suppression in cortisol concentration during the test, was diagnostic of pituitary-dependent hyperadrenocorticism (PDH). Mitch was referred to VCA West Los Angeles Animal Hospital to be evaluated for treatment.